<html>

<head>
	<meta charset="UTF-8"> 
	<style type="text/css">
		#myCanvas{
			border: 1px solid #ccc;
		}
	</style>
	<script type="text/javascript" src='js/jquery-1.11.1.js'></script>

	<script type="text/javascript">
		$().ready(function(){
			var canvas = document.getElementById("myCanvas");
			var context = canvas.getContext("2d");
			context.beginPath();
			context.arc(100,150,50,0,Math.PI * 2, true);
			context.stroke();

			context.beginPath();
			context.arc(210,150,50,0,Math.PI, true);
			context.stroke();

			context.beginPath();
			context.arc(320,150,50,Math.PI/2,-Math.PI/2, false);
			context.stroke();
		});

	</script>

    <title>Canvas 绘制圆、圆弧</title>
</head>

<body>
	<canvas id="myCanvas" width="400" height="300"></canvas>
</body>
</html>
